Automated extended depth of field imaging apparatus and method

ABSTRACT

An imaging apparatus and method enables an automated extended depth of field capability that automates and simplifies the process of creating extended depth of field images. An embodiment automates the acquisition of an image “stack” or sequence and stores metadata at the time of image acquisition that facilitates production of a composite image having an extended depth of field from at least a portion of the images in the acquired sequence. An embodiment allows a user to specify, either at the time of image capture or at the time the composite image is created, a range of distances that the user wishes to have in focus within the composite image. An embodiment provides an on-board capability to produce a composite, extended depth of field image from the image stack. One embodiment allows the user to import the image stack into an image-processing software application that produces the composite image.

CROSS REFERENCE TO RELATED APPLICATIONS

This Application claims benefit of U.S. provisional patent applicationSer. No. 61/034,088, filed Mar. 5, 2008, which is incorporated herein inits entirety by this reference thereto.

BACKGROUND OF THE INVENTION

1. Field of the Invention

In general the invention relates to extending the depth of field inimages. More particularly, the invention relates to an imagingapparatus, having an automated extended depth of field mode, andassociated method.

2. Background Information

Obtaining sufficient depth of field is a constant challenge inphotography, particularly when photographing at extremely close range orunder low lighting conditions. Setting the lens to a small apertureyields more depth of field, but this technique is eventually limited bydiffraction effects and may mandate excessively long exposure times. Thetraditional approach to this difficulty required the photographer todetermine the optimum lens aperture for effecting the golden meanbetween stopping down the lens for depth of field and opening it up forgood resolution. Close-up Photography & Photomacrography 78 (KodakTechnical Publication N-12, Eastman Kodak Co. 1977).

However, advances in image post-processing have enabled a new approachto this challenge. In extended depth of field (EDOF) photography, aphotographer captures a stack of images, sweeping the focus distance ofthe lens through the range of interest in a stepwise fashion.Post-processing software then combines the stack images into a singlecomposite image by selecting from each stack image the in-focus portionof the image. The resulting composite image thus provides both highresolution and a large depth of field. However, this technique requiresthe photographer to determine the depth of field provided by the lensand aperture, and to then manually advance the focus distance of thelens by the appropriate amount between acquisition of each stack image.This is both tedious and prone to error.

Software control programs are available that control camera systems toproduce image stacks, wherein each image is taken at different focuspoints within the subject. However, the software programs run externallyto the imaging apparatus, therefore requiring a separate computingapparatus, communicatively coupled to the imaging apparatus forexecuting the control software. Additionally, the task of mastering suchcontrol programs may be difficult and time-consuming. Furthermore, suchprograms are not widely available, typically being provided bymanufacturers or VAR's (value-added resellers) for specific imagingapparatus.

Digital cameras having an automated focus bracketing feature are nowavailable. In photography, “bracketing” is the general technique oftaking several shots of the same subject using different camerasettings. A camera having an automated focus bracketing capability takesa series of shots of a subject, automatically changing the focaldistance after each shot. Typically, the photographer may choose from anumber of settings that specify the number of shots. Such bracketingfeatures do not embody automated intelligence for calculating thespacing of images in a stack for (EDOF) photography based onphotographer-selected near and far focus limits.

SUMMARY

An imaging apparatus and method automates and simplifies the process ofcreating extended depth of field images. An embodiment automates theacquisition of an image stack and stores metadata at the time of imageacquisition that facilitates production of a composite image having anextended depth of field from at least a portion of the images in theacquired stack. An embodiment allows a user to specify, either at thetime of image capture or at the time the composite image is created, arange of distances that the user wishes to have in focus within thecomposite image. An embodiment provides an on-board capability toproduce a composite, extended depth of field image from the image stack.An embodiment allows the user to import the image stack into animage-processing software application that produces the composite image.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 provides a block diagram of a digital camera having an automated,extended depth-of-field mode;

FIG. 2 provides a flow diagram of a method for acquiring a stack ofimages having depths of field that span a predetermined distance rangefor production of extended depth-of-field (EDOF) images;

FIG. 3 provides a flow diagram of an alternate embodiment of a methodfor acquiring a stack of images having depths of field that span apredetermined distance range for production of EDOF images.

DETAILED DESCRIPTION

An imaging apparatus and method automates and simplifies the process ofcreating extended depth of field images. An embodiment automates theacquisition of an image stack and stores metadata at the time of imageacquisition that facilitates production of a composite image having anextended depth of field from at least a portion of the images in theacquired stack. An embodiment allows a user to specify, either at thetime of image capture or at the time the composite image is created, arange of distances that the user wishes to have in focus within thecomposite image. An embodiment provides an on-board capability toproduce a composite, extended depth of field image from the image stack.An embodiment allows the user to import the image stack into animage-processing software application that produces the composite image.

FIG. 1 shows a diagrammatic representation of a digital camera 100having an automated extended depth-of-field (EDOF) mode, according tothe invention.

The digital camera 100 includes a housing 102, a lens shutterarrangement system 104 having a focusable lens 106 and a shutter 108,and an image-sensing device 110, such as a CCD (charge-coupled device).One embodiment may include a camera setting adjustment system 114. Thecamera setting adjustment system 114 may include a stepper motor 112 forincrementally adjusting the focus distance of the lens 106 and the sizeof the aperture opening. Additionally, the camera setting adjustmentsystem may include an embedded system 116, the embedded system includingat least one processor and a motor driver for facilitating incrementalchanges in focus distance and aperture via the stepper motor 112.

In one embodiment, the digital camera may include both fixed focus andauto-focus modes. Selection of focus mode may be accomplished by meansof a switch (not shown) or by activating a focus mode-selectioncomponent in a user interface displayed on the LCD display 120. As shownin FIG. 1, the display is communicatively coupled to the embedded system116 by means of leads 122.

An embodiment allows the user to specify the range of distances at thetime of image capture. This may be done manually, for example, byselecting the defining distances via a pair of manual dials (not shown)or by selecting numerical values defining the range on the LCD display120, or in a camera-assisted manner by using the camera's autofocusfeature to specify the near and far limits of the range; for example bypointing a spot-metering range finder (within the auto-focus system ofthe camera) at two or more points of interest. Additional embodimentsmay employ, for example, weighted average metering or forms ofobject-class detection such as face detection to specify near and farlimits of the range. The camera then acquires a stack of images atspaced intervals sufficient to provide in-focus coverage across thedesired range, wherein the processor of the embedded system isprogrammed to control the process of acquiring an image stack forcreation of one or more EDOF images.

The foregoing description of an image capture apparatus is meant only tobe illustrative and is not intended to be limiting. In light of thepresent description, the ordinarily-skilled practitioner will understandthat other types of programmable image capture devices, for example,programmable film cameras, are entirely suitable for producing EDOFimages by the process described herein.

As above, the embedded system 116 includes at least one processor.Additionally, the embedded system includes a read-only memory havingstored therein one or more firmware modules for programming the at leastone processor to execute the steps of a process for producing EDOFimages as described herein.

In one embodiment, the embedded system may be composed of an ASIC(application specific integrated circuit) or one or more CMOSs(complementary metal oxide semiconductors). In other embodiments, thelogic component of the embedded system may be a microcontrollerprogrammed as below, or a FPGA (field programmable gate array) havinglogic circuits for performing the steps of the procedure below.

Referring now to FIG. 2, acquisition of the image stack begins with thecamera first approximating 202 the hyperfocal distance H:

$\begin{matrix}{H \approx \frac{f^{2}}{Nc}} & (1)\end{matrix}$

based on the f-number, N, the lens focal length, f, and the maximumpermissible circle of confusion c. The practitioner of ordinary skillwill appreciate that, in the fields of optics and photography,hyperfocal distance is is the closest distance at which the lens can befocused while keeping objects at infinity acceptably sharp. Theordinarily-skilled practitioner will understand that the maximumpermissible circle of confusion is the largest circle of confusionconsidered to provide acceptably sharp focus.

Then, beginning at one end of the specified range of distances, thefocus distances, s_(i), for the stack images are computed iterativelybased on approximations for the near and far limits—D^(n) and D^(f),respectively—of the depth of field:

$\begin{matrix}{{D^{n} \approx \frac{Hs}{H + s}}{and}} & (2) \\{D^{f} \approx {\frac{Hs}{H - s}.}} & (3)\end{matrix}$

For example, beginning at the far end of the specified range ofdistances, r^(f), the initial focus distance is computed by solving forthe focus distance in Equation 3 with D^(f)=r^(f). That is,

$\begin{matrix}{s_{1} = {\frac{{Hr}^{f}}{H + r^{f}}.}} & (4)\end{matrix}$

Then, the corresponding near depth of field limit is found usingEquation 2, namely:

$\begin{matrix}{D_{1}^{n} = {\frac{{Hs}_{1}}{H + s_{1}}.}} & (5)\end{matrix}$

The procedure is repeated with the near depth of field limit applied asthe far limit of the depth of field in the next iteration. Specifically,

$\begin{matrix}{s_{i} = \frac{{HD}_{i - 1}^{n}}{H + D_{i - 1}^{n}}} & (6) \\{{D_{i}^{n} = \frac{{Hs}_{i}}{H + s_{i}}},} & (7)\end{matrix}$

with D₀ ^(n)=r^(f). Substituting, the procedure can be summarized as

$\begin{matrix}{s_{1} = \frac{{Hr}^{f}}{H + r^{f}}} & (8) \\{s_{i} = {\frac{{Hs}_{i - 1}}{H + {2s_{i - 1}}}.}} & (9)\end{matrix}$

The iterative procedure continues until the near depth of field limit iswithin the near end of the specified range of distances. That is,iteration proceeds 204 until iteration N when D_(N) ^(n)≦r^(n).Equivalently, this occurs when

$\begin{matrix}{s_{N} \leq {\frac{{Hr}^{n}}{H - r^{n}}.}} & (10)\end{matrix}$

The result of the procedure is a stack of N images having abuttingdepths of field, covering the specified range of distances.

Of course, it is unlikely that the final image is at a focus distance,s_(N), with a near depth of field limit, D_(N) ^(n), corresponding tothe near end of the specified range of distances, r^(n). Most likely,the final image provides in-focus content nearer than r^(n). Anembodiment therefore preferably allows the user to specify whether hedesires to have at least the specified range of distances in focus orexactly the specified range of distances in focus. Based on thisspecification 206, the final focus distance may be adjusted. In theformer case, no adjustments need be made to the final focus distance.The result is a set of focus distances for a stack of images covering atleast the specified range of distances. Based on this set of focusdistances, the camera then obtains 208 a stack of N images havingabutting depths of field, covering at least the specified range ofdistances. In the latter case, the final focus distance is adjusted suchthat the near depth of field limit corresponds to the near end of thespecified range of distances 210, that is,

$\begin{matrix}{S_{N^{\prime}} = {\frac{{Hr}^{n}}{H - r^{n}}.}} & (11)\end{matrix}$

The result is a set of focus distances for a stack of images havingabutting depths of field covering exactly the specified range ofdistances. Based on this set of focus distances, the camera then obtains212 a stack of N images having abutting depths of field, coveringexactly the specified range of distances.

Alternatively, the images within the image stack may be acquired aftereach focus distance is calculated. In this embodiment, the adjustmentstep at block 210 may be performed by acquiring an additional image toreplace the final image of the stack already acquired.

EXAMPLE I

An exemplary calculation of focus distances according to the aboveprocedure proceeds as follows:

A photographer operating a camera and f=35 mm lens at N=4.0 specifies arange of distances r^(n)=5 m and r^(f)=25 m. The camera images using aCCD sensor characterized by a circle of confusion of c=6 μm. Then, fromEquation 1, H=51.04 m. Iterating according to Equations 8 and 9, thefocus distances are determined to be s₁=16.78 m, s₂=10.12 m, s₃=7.25 m,s₄=5.65 m and s₅=4.62 m. Iteration ceases in accordance with Equation 10with s₅≦5.54 m. As noted above, the final focus distance, s₅, mayoptionally be adjusted according to Equation 11 to s_(5′)=s_(N′)=5.54 m.

Alternatively, as shown in FIG. 3, it is possible to begin with the nearend of the specified range of distances. In this approach, the procedurecan be summarized as

$\begin{matrix}{s_{1} = \frac{{Hr}^{n}}{H - r^{n}}} & (12) \\{{s_{i} = \frac{{Hs}_{i - 1}}{H - {2s_{i - 1}}}},} & (13)\end{matrix}$

with termination upon

$\begin{matrix}{{s_{N} \geq \frac{{Hr}^{f}}{H + r^{f}}},} & (14)\end{matrix}$

and optional adjustment of the final image to

$\begin{matrix}{{s_{N^{\prime}} = \frac{{Hr}^{f}}{H + r^{f}}},} & (15)\end{matrix}$

as previously described with respect to FIG. 1. If the user does notspecify that the range of distances needs to be exact 306, the cameraobtains 308 a stack of images covering at least the specified rangeresults. If the user specifies that the range must be exact 306, thefocus distance of the final image is adjusted 310 so that the far depthof field limit corresponds to far end of the specified range ofdistances, and the camera obtains 312 a stack of images covering exactlythe specified range.

As with the process of FIG. 2, in an alternative embodiment, the imageswithin the image stack may be acquired after each focus distance iscalculated, and the adjustment step at block 310 may be performed byacquiring an additional image to replace the final image of the stackalready acquired.

EXAMPLE II

Again using the exemplary values of f=35 mm, N=4.0, r^(n)=5 m andr^(f)=25 m, and c=6 μm, and iterating according to Equations 12 and 13,the focus distances are determined to be s₁=5.54 m, s₂=7.08 m, s₃=9.80m, s₄=15.91 m, and s₅=42.24 m. Iteration ceases in accordance withEquation 14 with s₅≧16.78 m, and the final focus distance may optionallybe adjusted according to Equation 15 to s_(5′)=s_(N′)=16.78 m.

It is worth noting that the above procedures do allow the user tospecify a range of distances in which r^(f)=∞. In this case, in theinwardly-iterating procedure, the initial image is acquired at thehyperfocal distance. In the outwardly-iterating procedure, iteration isterminated when the focus distance exceeds the hyperfocal distance, andthe focus distance of the final image is optionally adjusted back to thehyperfocal distance.

The procedures—in particular, the termination criterion in the inwardlyiterating procedure and the initial image focus distance in theoutwardly iterating procedure—do become indeterminate should a userspecify a range of distances in which r^(n)>H. Such situations may behandled as special cases. For example, if the user requests that atleast the specified range of distance be in focus, the camera canacquire a single image at a focus distance s=H. If the user requeststhat exactly the specified range of distance be in focus, a warning maybe presented to the user prior to acquisition of a single image at s=H.

As can be seen, both the number and spacing of the stack images aredependent on the f-number. Preferably, the f-number is determinedautomatically by the camera using existing methods that consider, forexample, the capabilities of the lens and the light level. However, theinvention can also be used in conjunction with an aperture priority modein which the user may specify a specific f-number at which the stackimages are to be acquired. For example, a user willing to toleratereduced sharpness in the composite image could reduce the number ofstack images required by specifying a relatively small f-number. Thesystem may also allow the user to specify specific f-numbers for theindividual stack images, thus allowing customization of the stack imagespacing.

Similarly, the number and spacing of stack images is dependent on themaximum permissible circle of confusion c. Preferably, the value of c isselected automatically by the camera, based on the inherent limitations,i.e. the optical quality, of the lens, the capabilities, i.e. theresolution, of the imaging format (e.g. 35 mm film, CCD), and the amountof diffraction associated with the chosen f-number. Alternatively, thecircle of confusion may be specified by the user as desired. Forexample, a user willing to tolerate reduced sharpness in the compositeimage to reduce the number of stack images required could specify arelatively large maximum permissible circle of confusion.

In yet a further embodiment, the user can specify an overlap fraction, αof adjacent depths of field in the image stack. As in previousembodiments, hyperfocal distance and focus distances are calculated. Inthis case, however, the user specifies an overlap fraction. In thiscase, the procedures described herein above are modified such that thefocus distance of each image within the image stack is adjusted to placeone depth of field limit within the previous depth of field. Forexample, in the inwardly-iterating procedure, the focus distance(Equation 6) is adjusted to

$\begin{matrix}{s_{i} = \frac{{HD}_{i}^{f}}{H + D_{i}^{f}}} & (16)\end{matrix}$

where the far depth of field limit is within the previous depth of fieldas specified by α, namely,

D _(i) ^(f) =D _(i−1) ^(n)α(D _(i−1) ^(f) −D _(i−1) ^(n)).   (17)

Application of the overlap fraction results in a stack of images havingoverlapping depths of field. In the absence of an overlap fraction, astack of images having abutting depths of field results.

EXAMPLE Ill

Returning to the example above, with an overlap fraction of α=0.2,Equations 16 and 17 yield focus distances of s₁=16.78 m, s₂=11.65 m,s₃=8.78 m, s₄=7.00 m, s₅=5.81 m, and s₆=4.95 m and depths of field [D₁^(n),D₁ ^(f)]=[12.63 m, 25.00 m], [D₂ ²,D₂ ^(f)]=[9.49 m, 15.10 m], [D₃^(n),D₃ ^(f)]=[7.49 m, m, 10.61 m],[D₄ ^(n),D₄ ^(f)]=[6.16 m, 8.12 m],[D₅ ^(n),D₅ ^(f)]=[5.21 m, 6.55 m], and [D₆ ^(n),D₆ ^(f)]=[4.51 m, 5.48m].

A still further embodiment extends to multiple ranges of distance thatthe user wishes to have in focus. In this embodiment, each range can behandled separately, as described above.

In yet another embodiment, the user can specify one or more ranges ofdistances that he wishes to be out of focus. In this case, the out offocus ranges can be converted to one or more complementary in focusranges, each handled as described above.

Finally, in yet another embodiment, the camera automatically acquires astack of images providing coverage from the near field to infinity at anextremely small f-number. Because each image within the stack offers alimited depth of field, it is then possible for the photographer toselect, in post-processing software, what distances he would like tohave in focus and what regions he would like to have out of focus. Basedon the metadata saved by the camera for each image within the stack, thepost-processing software assembles the composite image from theappropriate images within the stack. This approach does require thecapture and storage of more stack images than may ultimately beutilized, but it does provide the photographer with greater artisticfreedom later in the production process.

Finally, the ordinarily-skilled practitioner will appreciate that theexpression in Equation 1 is only one possible approximation of thehyperfocal distance, and the expressions of Equations 2 and 3 are onlytwo possible approximations of the limits of the depth of field. Inparticular, these approximations are valid only for relatively largefocus distances in which s>>f. Especially in the case of extremely closesubject matter, such as in macrophotography, the depth of field may becalculated by any number of well known alternative approximations, anddifferent approximations may be used at different focus distances; inother words, different images within the stack.

The above procedures are preferably invoked by the user via selection ofan auto-EDOF mode, analogous to shutter priority or program modes foundon many cameras. For example, the user may select the mode on a rotarydial atop the camera. After selection of the mode and specification ofthe range of distances, the stack of images is preferably acquired asrapidly as possible in response to a single press of the shutter button.In the case of an SLR (single lens reflex) camera, the reflex mirror maybe held in a retracted position while the images are acquired. In thecase of a digital camera, the images may be written to a temporarymemory cache offering faster write times than the permanent memory,enabling faster image acquisition. Nonetheless, as the stack images arestill acquired over a span of time, the invention may be combined withany of several well-known techniques for digital image stabilizationthat are capable of backing out any motion of the subject or camera thatoccurs between successive images within the stack; for example the imagestack feature within PHOTOSHOP (ADOBE SYSTEMS, INC., San Jose, Calif.)or such image-processing software as HELICON FOCUS (HELICON SOFTWARE,LTD., Kharkov, Ukraine).

As noted above, the stack of images is combined into a single compositeimage during post-acquisition processing. In one embodiment, theprocessing is performed off-board the camera by a computational deviceprogrammed with an image processing software application for creatingextended depth of field images. Examples of such software applicationsare COMBINEZ5 and COMBINEZM, both open-source programs obtainable on theInternet, and both originally developed by Alan Hadley, a resident ofthe United Kingdom. To better facilitate post-processing operations, thecamera saves metadata with each image in the stack, preferablyindicating the inner and outer boundaries of the depth of field for theimage and the specified range of distances. At a minimum, the camerastores information from which these quantities can be determined, forexample the f-number, the lens focal length, and the maximum possiblecircle of confusion. The information is preferably stored in astandardized set of meta-data tags, such as those within theExchangeable Image File Format (EXIF).

In a further embodiment, the images may be combined into a singlecomposite image onboard the camera. In this case, the stack images maybe deleted after composition to increase available memory space.

The methods and systems herein described provide a large number ofunexpected benefits which render them a great advance over theconventional manner of producing extended depth of field images. Theforemost advantage provided by present methods and systems is that theyprovide an integrated solution to the challenge of producing extendeddepth of field (EDOF) images. Presently, practitioners in this art mustfirst acquire the images, largely, manually. The practitioner determinesthe depth of field boundaries and the corresponding depths of field atwhich it is necessary to acquire images in order to cover the desiredrange of distances. After acquiring the image stack, the practitionermust then export the image stack to a third-party software applicationwith which the composite, extended depth of field image is created.

The integrated solution provided by the present systems and methodsgreatly increases the ease with which such images may be produced. Untilnow, EDOF image production presented a formidable technical challengerequiring a high level of skill in the operation of imaging equipment,the integrated solution described herein reduces the level of requiredtechnical skill to approximately that required to operate a digitalcamera.

The present solution greatly simplifies the step of defining the focusrange for the EDOF image, substituting a simple, intuitive procedurewhereby the user defines the focus range by tagging successive focuspoints using the autofocus feature of a digital camera for thecumbersome manual procedure now generally used.

The present solution also greatly simplifies the acquisition of theimage stack. The system intelligently calculates the required depths offield to cover the specified range of distances and automaticallyacquires the image stack, with little or no additional user input. Oneembodiment integrates the production of the EDOF image, eliminating theneed for yet another software application to produce the image, andgreatly reducing the storage and transfer bandwidth requirementsinvolved in EDOF image production.

In the foregoing specification, the invention has been described withreference to specific exemplary embodiments thereof. It will, however,be evident that various modifications and changes may be made theretowithout departing from the broader spirit and scope of the invention asset forth in the appended claims. The specification and drawings are,accordingly, to be regarded in an illustrative sense rather than arestrictive sense.

1. A system for extended depth-of-field imaging, comprising: an imagingapparatus; at least one processing element integrated on said imagingapparatus; and storage means embodying program logic for automaticallyacquiring at least one stack of images having depths of field coveringat least one specified range of distances, wherein execution of saidprogram logic by said at least one processing element causes said systemto acquire said at least one stack of images.
 2. The system of claim 1,wherein said imaging apparatus comprises either a digital camera or afilm camera.
 3. The system of claim 1, further comprising a controlelement that enables a user to specify said range of distances, saidcontrol element comprising means for any of: specifying said at leastone range of distances directly; and specifying boundaries of at leastone out-of-focus range of distances, wherein an inverse of said at leastone out-of-focus range of distances comprises said at least onespecified range of distances.
 4. The system of claim 3, wherein saidcontrol element is operative to enable said user to specify said atleast one range of distances either before or after image acquisition.5. The system of claim 3, wherein said control element is selected fromthe group consisting of: one or more mechanical elements by which theuser specifies near and far distances defining said at least one rangeof distances; an integrated user interface wherein the user specifiessaid near and far distances defining said at least one range ofdistances by interacting with one or more elements within said userinterface; and an auto-focus system integrated within said apparatusthat includes means for said user to specify said at least one range ofdistances by pointing a range finder at successive points of interest.6. The system of claim 1, further comprising storage means embodyingprogram logic for creating at least one composite, extendeddepth-of-field image from at least a portion of said at least one stackof images.
 7. The system of claim 6, wherein execution of said programlogic for creating said at least one composite, extended depth-of-fieldimage by either said processing element integrated on said imagingapparatus or a processing element external to said imaging apparatuscauses said system to create said at least one extended depth-of-fieldimage from at least a portion of said at least one stack of images. 8.The system of claim 1, wherein said program logic for acquiring a stackof images having depths of field covering at least a specified range ofdistances comprises program logic for: iteratively computing a focusdistance for each stack image based on a hyperfocal distance and thenear and far limits of the at least one specified range of distancesuntil at least the specified range of distances is covered.
 9. Thesystem of claim 8, wherein a user is enabled to specify that the userwants to have exactly the specified range of distances in focus.
 10. Thesystem of claim 9, further comprising storage means embodying programlogic for adjusting the focus distance of a terminal image in said rangeof distances so that a depth of field limit for said terminal imagecorresponds to a specified limit of said specified range of distances.11. The system of claim 1, further comprising storage means embodyingprogram logic for any of: automatically determining f-number based onlens capabilities and light level; and automatically selecting a maximumpermissible circle of confusion.
 12. The system of claim 1, wherein eachof said depths of field covering at least one specified range ofdistances either overlap an adjacent depth of field or abut at least oneadjacent depth of field.
 13. The system of claim 1, further comprisingat least one selected from a group consisting of: control means for theuser to specify a specific f-number at which stack images are to beacquired; control means to specify specific f-numbers for individualstack images; and control means to specify a maximum permissible circleof confusion.
 14. The system of claim 1, further comprising: selectionmeans enabling said user to select an auto-EDOF mode from a plurality ofmodes, wherein acquisition of said stack of images proceedsautomatically after shutter activation.
 15. The system of claim 1,further comprising retraction means for retracting a reflex mirrorduring image acquisition.
 16. The system of claim 1, further comprisinga temporary cache offering faster write times than permanent memory,enabling faster image acquisition.
 17. The system of claim 1, furthercomprising a processor programmed to stabilize acquired images tocompensate for subject or camera movement during image acquisition. 18.A system for extended depth-of-field imaging comprising: an imagingapparatus; means integrated on said imaging apparatus for automaticallyacquiring at least one stack of images having depths of field coveringat least one specified range of distances.
 19. The system of claim 18,further comprising: means for creating at least one composite, extendeddepth-of-field image from at least a portion of said at least one stackof images.
 20. A method of operating an apparatus for extendeddepth-of-field imaging comprising the steps of: upon activation of acontrol element, at least one processing element within said apparatusfor extended depth-of-field imaging executing stored program logic forautomatically acquiring at least one stack of images having depths offield covering at least one specified range of distances; responsive tosaid step of executing said stored program logic, said apparatus forextended depth-of-field imaging automatically acquiring said stack ofimages having depths of field covering at least said specified range ofdistances.
 21. The method of claim 20, further comprising either of thesteps of: a user specifying said at least one range of distancesdirectly, either before or after image acquisition; and said userspecifying boundaries of at least one out-of-focus range of distances,either before or after image acquisition, wherein an inverse of said atleast one out-of-focus range of distances comprises said at least onespecified range of distances.
 22. The method of claim 20, wherein saidapparatus comprises either a digital camera or a film camera.
 23. Themethod of claim 20, further comprising the step of: automaticallycreating at least one composite, extended depth-of-field image from atleast a portion of said at least one stack of images.
 24. The method ofclaim 20, wherein acquiring said stack of images having depths of fieldcovering at least said specified range of distances comprises the stepsof: iteratively computing a focus distance for each stack image based onhyperfocal distance and the near and far limits of the specified rangeof distances until at least the specified range of distances is covered;and acquiring at least one image at each computed focus distance. 25.The method of claim 24, further comprising the step of: said userspecifying that the user wants to have exactly the specified range ofdistances in focus.
 26. The method of claim 25, further comprising thestep of: automatically adjusting the focus distance of a terminal imagein said range of distances so that a depth of field limit for saidterminal image corresponds to a specified limit of said specified rangeof distances.
 27. The method of claim 20, further comprising the stepsof: automatically determining f-number based on lens capabilities andlight level; and automatically selecting a maximum permissible circle ofconfusion.
 28. The method of claim 20, further comprising at least onestep selected from a group consisting of: a user specifying a specificf-number at which stack images are to be acquired; said user specifyingspecific f-numbers for individual stack images; and said user specifyinga maximum permissible circle of confusion.
 29. The method of claim 20,further comprising the step of: a user selecting an auto-EDOF mode froma plurality of modes, wherein acquisition of said stack of imagesproceeds automatically after shutter activation.
 30. The method of claim20, further comprising the step of: stabilizing acquired images tocompensate for subject or camera movement during image acquisition.